Apple Inc CEO Tim Cook on Thursday became the most prominent American corporate leader to come out as being gay, saying he was trading off his closely guarded privacy for the chance to help move forward civil rights.

The Alabama native, who has spoken out against discrimination of lesbian, gay, bisexual and transgender (LGBT) people, declared his sexual orientation in a magazine editorial, confirming a fact widely known in the close-knit Silicon Valley tech community but rarely discussed.

Cook's announcement comes as gay marriage is becoming widespread, but the nation is still divided over gay rights. Same-sex marriage is legal in thirty-two U.S. states and in polls a majority support same-sex marriage, with a clear generational divide between younger Americans who are more likely to support it and older ones who are less likely.

He invoked civil rights luminaries Robert F. Kennedy and Martin Luther King in his long essay.

"I don't pretend that writing this puts me in their league. All it does is allow me to look at those pictures and know that I'm doing my part, however small, to help others. We pave the sunlit path toward justice together, brick by brick. This is my brick."

The fact the chief executive of the most valuable U.S. publicly traded company felt he could disclose his sexual preference in such a public way, and with the backing of his company's chairman, shows how times have changed.

Former BP chief executive Lord Browne, who kept his sexual orientation secret for decades, was forced to come out after a boyfriend made it public in 2007. He later resigned.

"By deciding to speak publicly about his sexuality, Tim Cook has become a role model, and will speed up changes in the corporate world," Browne said in an email to Reuters on Thursday.

EFFECT ON BUSINESS

It remains to be seen whether Cook's disclosure will affect the company's business in conservative markets such as Russia, Iran and parts of Africa. Apple now gets more than half of its revenue from abroad, with China its second largest single market.

Cook said his desire for personal privacy had held him back. Even in the United States, is not necessarily an easy decision to be open about being gay, civil rights advocates say.

"As the first CEO of a Fortune 500 company to reveal he is gay, Tim helps make the business world a bit less homophobic," Marianne Duddy-Burke, executive director of gay rights organization DignityUSA told Reuters in an email.

"I'm sure this will make it easier for some others in similar positions to consider coming out."

While never broadcasting his sexual orientation, Cook has frequently spoken out against discrimination of the LGBT community, most recently this month when he addressed a group in his native Alabama.